The purpose of the present investigation will be to study in children the impact of protein calorie malnutrition (PCM), iron deficiency and infection on the metabolic capacity of blood polymorphonuclear leukocytes (PMN) as well as on its phagocytic and bactericidal capacity. These functions will be measured by means of oxygen uptake on resting conditions and during phagocytosis, bacterial ingestion and killing and assays of the myeloperoxidase system. The micro-organisms to be used are Staphylococcus and Candida. Any derangement found will be identified in terms of intracellular location and specific enzyme affected.